1. Field of the Invention
This invention relates in general to automated storage and retrieval systems, and more particularly to an input/output periscope station for automated storage and retrieval systems.
2. Description of the Related Art
In an automated information storage and retrieval system, also known as an automated library, numerous slots, or storage cells, are arrayed within the library. These storage cells are used to hold information media that are portable or removable from the library, such as magnetic tape cartridges or optical disks. The term "cartridge" used herein refers to any retaining structure for such removable information media. Although the present invention is described herein with respect to a magnetic tape library storing tape cartridges, it is not so limited but is equally applicable, for example, to an optical library holding optical disk cartridges, cartridge-less optical disks, optical tape cartridges, even magnetic disk cartridges or diskettes, and the like. The storage cells typically have an opening in the front to allow the cartridge to be inserted or removed.
A library typically includes a controller, an accessor, a drive, and an Input/Output station. The library controller directs the actions of the other library components. The library controller can also connect to a host processor and respond to control commands from the host processor. The library controller inventories the storage cells noting the identity of each cartridge occupying a storage cell. If no cartridge is situated in a particular storage cell, the library controller records this storage cell as empty. Typically, each cartridge has a unique identifying mark, such as a bar code label, on an edge of the cartridge visible through the cell opening.
The accessor transports a selected cartridge between its origin and its destination. A storage cell, a drive, and the Input/Output station serve as origins and/or destinations. The accessor grips the cartridge with a holding device. The accessor may also be equipped with a vision system, such as a bar code reader, to read the label on a storage cell when the accessor is positioned near the storage cell. During an inventory of the library, such as when a new library has been installed, the vision system scans the cells and reports to the library controller the identity of stored cartridges and their location within the array of storage cells. The library controller records the identity and location information in a database. The library controller later refers to and updates this database when a cartridge is moved between an origin and a destination. In this sense, the library controller must "know" the identity of each cartridge and its location within the array of cells in order to be able to retrieve the cartridge for access.
Libraries also have one or more drives to read data from a tape cartridge or write data to a tape cartridge. The accessor removes a selected tape cartridge from a storage cell and inserts it into the drive. Once in the drive, data can be read from the tape cartridge and sent to the host processor. In some library configurations, the data is sent to the host processor through the library controller. Whereas, in other library configurations the data is transferred directly from the drive to the host processor. In this latter configuration, the library controller sends a response to the host processor indicating the selected cartridge is placed in the drive. The host processor then issues a command to the drive to transfer the data. Likewise, data can be written from the host processor to the drive in either library configuration. In both configurations, the library controller directs the accessor to load the selected cartridge into the drive before the data is written to the cartridge.
Libraries also typically include an Input/Output station and an operator panel. The Input/Output station is a port through which a system operator can pass a cartridge to be added to the storage array or through which the accessor can pass a cartridge to the operator for removal from the storage array. The operator panel provides a communication mechanism for an operator to make requests to add cartridges to the library or remove cartridges from the library. The Input/Output station allows the operator to change cartridges in the storage array without requiring the library controller to inventory the entire storage array. Typically, an inventory must be taken each time a library access door is opened by the operator since it is not known whether the operator has added cartridges to the array, has removed cartridges from the library, or has not altered the contents of the library at all. The term library access door refers to a door in the library large enough to allow the operator to manually insert or remove cartridges into the storage cells of the storage array. The library access door does not refer to a door which provides the operator access to the Input/Output station.
As stated before, an inventory of the library may require the vision system of the accessor to scan all the storage cells in the storage array and report to the library controller the identity of stored cartridges and their location within the array of storage cells. If a cartridge label cannot be detected or read when the accessor is near a storage cell, that cell is recorded as empty. The vision system may also mistakenly classify a cell as being empty when, in fact, the cell is actually occupied. For example, a cartridge may occupy the cell but have an unreadable label, or even no label. A cartridge may be improperly oriented within the cell or a foreign object may occupy the cell. If the accessor attempts to insert a cartridge into such an occupied cell, an error condition will result causing a time consuming error recovery procedure to be initiated.
One known error procedure attempts to reduce such non-empty errors by directing the accessor's gripper to attempt to reach inside every cell which does not have an identifiable cartridge and verify by "touch" that the cell is actually empty. Any cell which is still not found to be empty is classified in the database as having an "occupied but invalid" status to prevent its use. An inventory of a 400 cell library, for example, can take three or four hours to complete using this procedure.
The Input/Output station saves time and increases the overall performance of the library. Instead of requiring an operator to manually insert or remove cartridges to or from the storage cells, an operator can use the Input/Output station. The accessor then transports a cartridge to or from the storage cell within the storage array. Additionally, the accessor can transport cartridges directly to the drive from the Input/Output station. The vision system in the accessor automatically reads the label on the cartridge. The library controller then adds the identity and location of the cartridge to the inventory database. Without the Input/Output station, an operator would have to open a library access door to simply add or remove a single cartridge. The opening of the library access door would cause the library to inventory the entire storage array when its contents would have only changed by a single cartridge.
The Input/Output station can still prevent the library from achieving its highest level of performance. An Input/Output station design that interferes with the path of the accessor would require the accessor to be paused any time the Input/Output station was used. Pausing the accessor causes the automated processes within the library to be suspended during use of the Input/Output station. Suspension of these automated processes in turn slows down the library performance. Alternatively, some current Input/Output station designs do not interfere with the path of the accessor. Typically, these Input/Output stations are located in the front panel of the library and use a rotary mechanism to pass a cartridge from the exterior to the interior of the library. The Input/Output station pivots the cartridge 180 degrees such that the cartridge label faces both the operator and the accessor when either is handling the cartridge. This Input/Output station design requires the accessor to pivot. This pivoting motion can slow down the performance of the accessor when transporting the cartridge to a storage cell within the storage array.
In addition, new libraries are being developed which are relatively small in size. An Input/Output station located in the front panel of the library is inconveniently low for an operator. An Input/Output station which allows the operator to insert cartridges into or remove cartridges from the top surface is much more convenient in smaller libraries. Also, an Input/Output station which does not require the accessor to pivot can decrease the time to transport the cartridge between the Input/Output station and the storage array and increase the overall performance of the library.
Existing libraries have their I/O station slanted and require a push down action after a cartridge is imported or exported. This I/O station cannot be used by other robots or autochangers to automatically exchange cartridges from their shelves into the this type of library. Today there are robots that use an old style optical library I/O station to import and export cartridges, and the library I/O station is horizontal and does not require a close down action after cartridge insertion.
It can be seen then that there is a need for a periscoping I/O station that provides a push down action after a cartridge is imported or exported.
It can also be seen then that there is a need for a periscoping I/O station that can be used to automatically exchange cartridges with adjacent libraries.